The present invention relates to a membrane button key structure for electronic devices and particularly a membrane button key structure with a built-in speaker.
Due to continuous innovations of electronic techniques and rapid developments of digital technologies, 3C information products have become indispensable outfits and helpful working tools for many people. 3C information products include notebook computers, mobile phones, personal digital assistants (PDAs), Palm computers (Palms) and the like. PDA, because of its powerful functions, user-friendliness and light and compact size, has been widely accepted by consumers. In addition, PDA can also include many other functions such as to access the Internet in a wireless fashion, communication, and video/audio enabling. It has becomes a prevailing trend of the information product development nowadays.
Refer to FIG. 1 for a conventional PDA. It includes a casing 10, a display panel 12 and a membrane key 14. The casing 10 has a plurality of openings formed on the surface to match and accommodate the display panel 12 and the membrane key 14. The keys 140 of the membrane key 14 are extending above the openings. Users can depress the keys 140 to perform the operations of the PDA. The information are displayed on the display panel 12.
Refer to FIG. 2 for the membrane key of adopted by conventional techniques. The membrane key 20 includes a four-way key 21 and a plurality of hot keys 22. The keys 21 and 22 are interconnected by a membrane 23. The entire membrane key 20 is integrally formed from a pliable rubber. The four-way key 21 has four bulged points 24 located on a lower side of four corners. Each hot key 22 also has a bulged point 22 located thereunder. There is a circuit board 25 located below the membrane key 20. The circuit board 25 has a plurality of touch switches 26 located on the surface thereof. The bulged points 24 below the keys 21 and 22 correspond to the touch switches 26 of the circuit board 25. Users may enter input commands on the PDA by depressing the keys 21 and 22 to move the bulged points 24 located therebelow in contact with the touch switches 26 of the circuit board 25. The input commands are processed and the results are displayed on the display panel (not shown in the drawings).
These days, PDA equipped with video/audio or mobile phone capabilities has become a hotly pursued trend. One of the critical elements to achieve the aforesaid functions is the speaker. To make the PDA competitive, it must by lean and light, and has a big enough display screen. To meet those requirements, conventional techniques of PDA have fully utilized the internal space of the casing for the configuration of the necessary elements and keys. It is very difficult to allocate an additional space for the speaker. When trying to adopt the conventional techniques to add the speaker on the front side of the PDA without increasing the total size, the size of the display panel has to be shrunk. To keep the speaker on the front side of the PDA without reducing the size of the display panel, total size of the PDA should be increased. To install the speaker on the rear side of the PDA will increase the total thickness. Besides, when the speaker is located on the rear side of the PDA, the audio quality is not desirable. When it is coupled with the mobile phone, the voice output from the rear side has the risk of being eavesdropped.
Because of the conventional techniques have difficulty to include the speaker in the PDA and still meet the requirements of lean and light and a large enough display screen, it is necessary to develop new techniques to resolve the problem.
Therefore the primary object of the invention is to provide a membrane button key structure with a built-in speaker to offer PDAs or the related electronic products with audio function without increasing the thickness and size of the product, or reducing the size of the display screen.
The membrane button key structure with a built-in speaker of the invention is adopted for use on PDAs or the related electronic products. The PDA includes a circuit board which has a plurality of touch switches and a carved opening on the surface thereof. The invention includes a membrane key, a bottom lid and a speaker. The membrane key consists of a four-way key and a plurality of hot keys interconnected by a membrane which is integrally made from a pliable rubber. The four-way key has four bulged points located on bottom side of four corners. Each hot key also has a bulged point located on the bottom in the center thereof. When the membrane key is coupled above the circuit board, each key located under the membrane key corresponds to a touch switch of the circuit board. The center of the four-way key is above the carved opening. The bottom lid is under the carved opening and forms a housing compartment with the four-way key for housing the speaker in the middle thereof. The space between the speaker and the four-way key becomes an upper acoustic chest and the space between the speaker and the bottom lid becomes a lower acoustic chest.
The invention aims at installing the speaker below the four-way key of the membrane key without increasing the total thickness and size of the PDA, or reducing the size of the display screen. The circuit board below the four-way key is properly carved to coupled with a bottom lid to form a housing compartment with the four-way key. Therefore, the speaker may be installed in the PDA to generate a desired audio effect without increasing the total thickness and size of the PDA, or reducing the size of the display screen. In order to form the carved opening on the circuit board, the circuit layout on the circuit board has to be properly designed to prevent from being interrupted. In addition, the interior of the four-way key and function keys is formed in a hollow manner to increase the acoustic space of the acoustic chest to improve the sound quality of the speaker. The bulged points to contact the touch switches of the circuit board are maintained. The membrane connecting the keys has troughs formed on the bottom thereof to communicate with the hollow space of the hollow keys so that the space of the acoustic chest may be increased to improve the sound quality of the speaker.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.